Evaluation of Heterosis and Heritability of Quantitative Traits and Grouping of New Cultivars and Genotypes of Fennel (Foeniculum vulgare. Mill)

Fennel is a cross-pollinating plant and one of the most important medicinal plants of the Apiaceae family, whose essential oil is widely used in various pharmaceutical, food, and cosmetic industries. Fennel originated from the Mediterranean region and is a biennial or perennial species. Fennel essential oil has been demonstrated to have antioxidant, anti-cancer, antibacterial, antifungal, and analgesic effects. Improving yield is one of the important goals of breeding, and the use of heterosis as one of the powerful tools to improve yield has always been of interest to breeders. This study was conducted to evaluate seed yield and yield components of three synthetic cultivars of fennel and compere with eight parental populations.

To investigate the yield, yield components, and the degree of heterosis of important traits of breeding fennel cultivars, three synthetic cultivars along with eight superior parents were investigated in the form of a randomized complete block design. The experiment was conducted in the spring of 2019 in the research field of the College of Aburaihan, University of Tehran, located in Pakdasht. During the growing period and after harvest the traits such as no. umbel, number of nodes, no. umbellets per umbel, no. seed per umbel, harvest index,  seed yield per plant, plant biomass, 1000 seed weight, essential oil content, essential oil yield, and seed yield were measured in the 50% flowering stage. Analysis of variances was done and a comparison of means was performed by Duncan٬s multiple range at a five percent probability level. Heterosis, Heritability of traits, and some genetic parameters of the traits in fennel genotypes were calculated. To determine the genetic distance and grouping of genotypes, principal component analysis, and cluster analysis were performed. All analyses were carried out using the SAS and Statgraphics software.

Based on the results of the analysis of variance, the differences between the studied genotypes were significant for all traits. Medium and late synthetic cultivars had significantly higher seed yield and essential oil yield than other genotypes and their yield heterosis rate was positive compared to the average of parents and was 39% and 38%, respectively. Evaluation of heterosis rate showed that cultivars Synthetics were superior to parents in most traits. General heritability for different traits was estimated to be between 34% and 93%. In this study, the phenotypic variation coefficients of all traits were higher than the genetic variation coefficients, which indicated the existence of environmental factors for these traits The results showed that principal components that the first four components account for more than 90% of the total variance changes. Based on the cluster, genotypes were divided into four groups. It could be expected that these synthetic cultivars can be introduced and expanded in the market of medicinal plants after being registered as commercial cultivars.

In general, the results of this study indicated that the mean squares of the parents against synthetic cultivars were significant for most of the traits, indicating the occurrence of heterosis in these traits. The results showed that the heterosis of most traits of synthetic cultivars was additive and positive. The highest percentage of heterosis compared to parents was for seed yield, essential oil yield, and the number of umbrellas per plant. It also seems that the traits related to yield components have higher heritability than other traits. The results showed that the synthetic cultivars were superior to their parent genotypes in terms of seed yield and essential oil yield. As a result, it should be said that the breeding method of creating synthetic cultivars in the fennel plant is successful. It can be expected that these synthetic cultivars could be introduced and expanded in the market of medicinal plants after being registered as commercial cultivars.